One conventionally known type of a mechanical seal having a spring on the rotating side for adding seal area pressure, represents a structure shown in FIG. 8 where a stationary-side seal ring 32 is hermetically fitted via a cup gasket 31 into an engagement concave area 52 formed at the opening of a shaft hole 51 of a housing 30, while a rotating-side seal ring 33 placed on the outer periphery of a rotational shaft 50 in a manner freely movable in the axial direction is pressed against the stationary-side seal ring 32 by the axial-direction bias force of a coil spring 41 backed with a collar 40 in order to form a sealing face S, and a bellows 45 that functions as an actuating shaft gasket is present between the outer periphery face of the rotational shaft 50 and a back face 33a of the rotating-side seal ring 33 and a space between the rotating-side seal ring 33 and rotational shaft 50 is sealed with the bellows 45 (hereinafter referred to as “background art”; refer to Patent Literatures 1 and 2, for example).
The mechanical seal pertaining to the aforementioned background art is such that a tip neck area 45a of the bellows 45 whose section has a sickle neck shape is fixed to the inner side of the back face area 46a of a metal case 46 fitted to the outer periphery of the rotating-side seal ring 33 and thus contacts the back face 33a of the rotating-side seal ring 33, while an inner-diameter cylinder area 45b of the bellows 45 is tightened by a metal drive ring 47 fitted to its outer periphery face and press-fitted, with an appropriate interference, onto the outer periphery face of the rotational shaft 50.
A projection 46c extending in the axial direction is provided on the inner-diameter side of the back face area 46a of the case 46 and this projection 46c engages, with play, with a cutout groove 47a formed on the outer periphery face of the drive ring 47 and extending in the axial direction, while a caved-in area 46e formed on an outer-diameter cylinder area 46d of the case 46 engages with a concave area 33b formed on the outer periphery face of the rotating-side seal ring 33. In other words, the rotating-side seal ring 33 receives the drive force from the rotational shaft 50 via the inner-diameter cylinder area 45b of the bellows 45, cutout groove 47a of the drive ring 47, projection 46c of the case 46, and caved-in area 46e of the case 46, and rotates with the rotational shaft 50.
With such mechanical seal, the following two methods are known as means for joining the rotating-side seal ring 33 as one piece with the bellows 45 or other member on the rotating side:    First means: As shown in FIGS. 8 (b) and (c), the tip of the rotating-side seal ring 33 on the outer-diameter cylinder area 46d of the case 46 is clinched toward the inner-diameter side to form a bent area 46f, and a surface 33c of the rotating-side seal ring 33 is wrapped with the bent area 46f.     Second means: Non-drying adhesive, etc., is applied between the back face 33a of the rotating-side seal ring 33 and a seal area 45c of the bellows 45 to lock the rotating-side seal ring 33 to the bellows 45.
However, the aforementioned first means presents a problem in that, although inherently the bent area 46f is structurally prevented from contacting the surface 33c of the rotating-side seal ring 33, it may be clinched excessively as shown in FIG. 8 (b), or a condition may occur where the bent area 46f is clinched normally but makes strong contact with the surface 33c of the rotating-side seal ring 33 as shown in FIG. 8 (c), depending on the clinching jig, clinching conditions, finished dimensions of the component members on the rotating side (rotating-side seal ring 33, bellows 45, drive ring 47 and case 46), etc., in which case the rotating-side seal ring 33 may distort or crack.
On the other hand, the aforementioned second means, which involves applying non-drying adhesive between the back face 33a of the rotating-side seal ring 33 and the seal area 45c of the bellows 45 to adhere the two, presents a problem in that evenly applying the adhesive is difficult and areas of unevenly applied adhesive are created, causing the sealed fluid to leak from between the back face 33a of the rotating-side seal ring 33 and the seal area 45c of the bellows 45, or causing the non-drying adhesive to attach to/enter the sealing face S, resulting in higher torque or starting problem.